Sputtering apparatus of the type with which the invention is concerned generally comprises a vessel which is capable of being sealed from the ambient atmosphere so that it can be pumped down and background gas admitted thereto. Inside the vessel there are provided anode means and cathode means spaced apart by a sputtering gap. The target material which is to be sputtered is built into portions of the cathode means which face the anode and a substrate is moved over the anode to capture material which is driven out of the cathode means by the sputtering process.
In the sputtering process, after the vessel has been evacuated, a background gas in the form of a heavy inert gas such as argon is admitted. A high electric field, preferably an RF field of several thousand volts at a frequency of 13.56MH is applied across the gap between the anode and the cathode and this ionizes the inert gas. The heavy ions bombard the target and drive target material in the form of molecules or atoms out of the target, such particles flying across the intervening gap toward the anode and impinging against the substrate.
Cathode materials are often used which are reactive with oxygen. Thus, if a vessel is open to the ambient atmosphere for purposes of recharging, the cathode materials may very well be contaminated by the oxygen and thereby be rendered inefficient or even inoperative. Likewise, pollutants and moisture may enter during the period of time that the vessel is open and thereby contaminate the target.
The invention herein solves this problem by closing off the targets and sealing them when it is desired to open the vessel, thereby preventing contamination thereof.